AFCI on Bath Exhaust Fan

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BMacky

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Foster City, CA
I have a customer whose home was wired by either an inexpensive (you get what you pay for) or inexperienced electrical contractor or DIY general contractor. Regardless, I continue to find issues with this house after correcting 41 of the 65 inspection violations that the private inspector, hired by the homeowner, came across during his very thorough inspection.

Recently, I was called to handle "lights going out" when they took showers and had the exhaust fan running. I figured it was a GFCI issue and took a look. What I found was that the bath, bedroom and dining room circuits (lighting/fan and power) other than the required 20A receptacle at the basin were all on an arc fault breaker. I've been trying to isolate the source of the possible "nuisance" tripping or other arcing that may be occurring on this circuit.

Question: Are arc fault breakers known for nuisance tripping in cases like this where it's possible moisture in the fan is getting across some terminations in a modular plug, or even the motor, and causing the problem?

Bigger Question: I heard that, but have yet to verify, arc fault breakers are going to be required in bath circuits including fans. I see a potential for nuisance tripping in this case, if it is just a moisture issue.

FYI: this is a very small bathroom and the shower is close to 40% of the space. Lots of condensate and a 110 CFM fan, which I am probably going to replace with a larger capacity unit.

Anyone with similar scenario and advice please comment. I don't want to replace the unit and have the same thing happen again.

Thanks!
 
210.12(B) of the 2008 does not list bathrooms are being required to be AFCId. Does the circuit supplying the fan go anywhere else that does require AFCI?

Better yet, is the '08 even enforced there yet? HIs are notorious for not knowing the code, let alone which edition is used.
 
AFCI on bath exhaust fan

AFCI on bath exhaust fan

480sparky said:
210.12(B) of the 2008 does not list bathrooms are being required to be AFCId. Does the circuit supplying the fan go anywhere else that does require AFCI?

Better yet, is the '08 even enforced there yet? HIs are notorious for not knowing the code, let alone which edition is used.
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The circuit covers bath lighting, master bedroom lighting/receptacles as well as dining room receptacles on a shared wall with the master bedroom. There's another no-no I uncovered while t/s this issue.

2008 NEC is not being enforced. I thought I'd separate the fan and put it on a different circuit but it looks like to do this I need to go back to the panel. The existing branch circuit wiring is 14 gauge and the nearest optional source is the bath 20A required circuit.
 
480 sparky said:
Does the circuit supplying the fan go anywhere else that does require AFCI?
Click to expand...


BMacky said:
Recently, I was called to handle "lights going out" when they took showers and had the exhaust fan running. I figured it was a GFCI issue and took a look. What I found was that the bath, bedroom and dining room circuits (lighting/fan and power) other than the required 20A receptacle at the basin were all on an arc fault breaker. I've been trying to isolate the source of the possible "nuisance" tripping or other arcing that may be occurring on this circuit.
Click to expand...

I could be wrong, but I read OP and thought the he meant that bath, bedroom, and dining room were all on one arc fault breaker.

If there only one bathroom in the dwelling, perhaps he could move the wiring from the fan to the bath GFCI receptacle. This would satisfy the '05 code and get the fan off the AFCI breaker.

EDIT: for quote marks
 
BMacky said:
Question: Are arc fault breakers known for nuisance tripping in cases like this where it's possible moisture in the fan is getting across some terminations in a modular plug, or even the motor, and causing the problem?
Bigger Question: I heard that, but have yet to verify, arc fault breakers are going to be required in bath circuits including fans. I see a potential for nuisance tripping in this case, if it is just a moisture issue.

FYI: this is a very small bathroom and the shower is close to 40% of the space. Lots of condensate and a 110 CFM fan, which I am probably going to replace with a larger capacity unit.
Anyone with similar scenario and advice please comment. I don't want to replace the unit and have the same thing happen again.

Thanks!
Click to expand...


I think you are right on target with the fan motor, all most all of the "nuisance" tripping I have seen on AFCI's has been motor related.
If you can just swap out the motor/ fan guts and see if that fixes the problem. Many motors are supplied by the cheapest supplier and are not very good , vacuums are one of the more common problems along with fans.
 
I've done hundreds of new homes with a good many of them done to the code minimum. As a matter of course all lighting in the bedroom areas will be on one of the AFCI circuits. It would not make sense to pull a separate circuit for just a hall, two bath lights and the attic keyless. The bath recpts are typically daisy chained in these situations so that circuit is not an option. Bath fans on arc-faults typically have not caused me much grief. I have used Cutler Hammer BR and CH, GE, Square D both Homeline and QO and have had good results with all of them.

With that out of the way, as far as I understand an AFCI breaker does have GFCI protection albeit at a higher threshold somewhere in the 30ma range. If your customer has a habit of taking long showers and steaming up the room that could be an issue. Poor installation of the ductwork could also contribute to this. Condensation running back from the duct into the fan housing and collecting on the connector can be a problem too, especially if the duct runs through an unconditioned space such as the attic. If that is a problem make sure that there is some sort of a "trap" in the duct for the moisture to collect. This could be as simple as a dip in the flex right after the adapter to the housing.

As a last resort with no other circuit available, you may have to consider a remote fan. Placed in the attic space the moisture in the bathroom will not be an issue and it will provide quieter operation. you could also vent both bathrooms with one fan.

Good luck,
FRANK

edited to add comment
 
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BMacky said:
FYI: this is a very small bathroom and the shower is close to 40% of the space. Lots of condensate and a 110 CFM fan, which I am probably going to replace with a larger capacity unit.
Click to expand...

If it is such a small bathroom there should be no need to go with a larger fan.
 
electricmanscott said:
If it is such a small bathroom there should be no need to go with a larger fan.
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I tend to agree,. remember a fan can only move air,. if it has air to move,.. I have had customers call me and question why the very expensive ,very quiet, properly sized exhaust fan does not seem to exhaust. Many times ,..with the door closed there is no way for the 110 cubes of air to enter the room in one minuet to be exhausted by the fan .

no air ,,..no exhaust
 
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